644778518411 has 2 divisors, whose sum is σ = 644778518412. Its totient is φ = 644778518410.

The previous prime is 644778518399. The next prime is 644778518441. The reversal of 644778518411 is 114815877446.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 644778518411 - 2²⁶ = 644711409547 is a prime.

It is not a weakly prime, because it can be changed into another prime (644778518441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322389259205 + 322389259206.

It is an arithmetic number, because the mean of its divisors is an integer number (322389259206).

Almost surely, 2^644778518411 is an apocalyptic number.

644778518411 is a deficient number, since it is larger than the sum of its proper divisors (1).

644778518411 is an equidigital number, since it uses as much as digits as its factorization.

644778518411 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6021120, while the sum is 56.

The spelling of 644778518411 in words is "six hundred forty-four billion, seven hundred seventy-eight million, five hundred eighteen thousand, four hundred eleven".